Melatonin in Skincare: Circadian Antioxidant Science, Melanogenesis Modulation & 2026 Clinical Evidence

When Aaron Lerner isolated melatonin in 1958, he did not discover it through sleep research — he found it because it lightened amphibian melanophores. The “pineal factor” that would later define our understanding of circadian rhythm was, first and foremost, a pigment molecule. Nearly seven decades later, that origin story has become surprisingly relevant: in 2026, melatonin is one of the most actively researched topical ingredients in skin science, with a genuine cutaneous biology that extends far beyond the pineal gland.

This review examines what the peer-reviewed evidence actually supports — the mechanisms, the clinical trials, and the significant open questions that formulators should understand before building a melatonin-based product.

The Cutaneous Melatoninergic System

Human skin is not merely a target for circulating melatonin; it is a complete, autonomous melatonin-producing organ. Slominski and colleagues demonstrated that the full serotoninergic and melatoninergic machinery — including the rate-limiting enzymes for melatonin synthesis — is expressed in human skin cells, and that keratinocytes, melanocytes, and fibroblasts produce melatonin locally (Slominski et al., J Invest Dermatol, 2018).

Melatonin acts through two G-protein-coupled receptors, MT1 and MT2. In human skin, MT1 is the predominant receptor subtype in both whole tissue and cultured cells, with MT2 also present and upregulated in response to UVB (Slominski et al., 2005). Critically, many of melatonin’s cutaneous effects are receptor-independent — it is both water- and lipid-soluble, which allows it to penetrate cellular membranes, accumulate in mitochondria, and quench reactive oxygen species directly at their source.

This dual pharmacology — receptor-mediated signaling plus direct intracellular antioxidant chemistry — is what makes melatonin mechanistically distinct from conventional antioxidants such as vitamin C or E.

Mechanism 1: Mitochondrial Antioxidant and Photoprotection

Melatonin’s most robustly established skin function is photoprotection. Because it is highly lipophilic, it reaches the mitochondrial matrix where UV-induced ROS are generated, and it also upregulates phase-2 antioxidant enzymes — γ-GCS, HO-1, and NQO1 — through the Keap1-Nrf2 pathway (Kleszczynski, J Pineal Res, 2013). Its metabolites, including AFMK and 5-methoxytryptamine, can be even stronger radical scavengers than melatonin itself.

A critical nuance: melatonin’s UV absorbance peaks at 225–275 nm, well below the UVA/UVB range of 290–390 nm. It therefore does not act as a sunscreen filter. Its protection is entirely a consequence of ROS quenching and antioxidant-enzyme induction.

The landmark timing study by Bangha and colleagues (Dermatology, 1997) treated 20 volunteers with 0.6 mg/cm² of melatonin in a nanocolloid gel at defined intervals around UV exposure. Applied 15 minutes before irradiation, melatonin almost completely suppressed erythema development; applied 1, 30, or 240 minutes after irradiation, the protective effect disappeared. A subsequent double-blind study established a clear dose-response: 12.5% melatonin cream protected against sunlight-induced erythema, while 0.5% and 2.5% formulations did not differ significantly from placebo.

Mechanism 2: Melanogenesis Modulation — The Contested Science

Melatonin’s effect on pigmentation is where the evidence becomes genuinely interesting — and genuinely unresolved. A 2022 review by Sevilla, Slominski, and Paus (J Pineal Res) synthesized the human melanocyte data and concluded that melatonin and its metabolites inhibit both melanogenesis (via reduced tyrosinase activity) and melanocyte proliferation, acting through MT1/MT2 receptors and downstream pathways involving Nrf2/PI3K-AKT, MC1R-cAMP signaling, and the pigmentation clock genes Bmal1 and Per1.

A 2023 mechanistic study (Int J Mol Sci) treating amelanotic and melanotic human melanoma cells with melatonin and its metabolites (AFMK, 5-MT, 6-OH-melatonin) found a significant reduction in cyclic AMP, MITF expression, and tyrosinase activity — with a receptor-independent mechanism, since MT1/MT2 antagonists (luzindole, 4-P-PDOT) failed to block the effect.

Yet the picture is not one-directional. A 2023 Experimental Dermatology study on human eyelid epidermis reported concentration-dependent stimulation of melanin production by melatonin, and earlier work in SK-Mel-28 melanoma cells showed melanogenesis activation rather than inhibition. The likely resolution is that melatonin’s pigmentary effect is biphasic — dose-, vehicle-, and tissue-context-dependent — and that most current data derive from melanoma cell lines or ex vivo epidermis rather than controlled human pigmentary trials. This is the central open question of the field, and any formulator making brightening claims must account for it.

Clinical Evidence: What Controlled Trials Actually Show

The strongest human data support photoprotection and anti-aging parameters, not pigmentary endpoints.

• Photoprotection (Bangha 1997; Dreher 1998): Statistically significant, dose-dependent reduction of UV-induced erythema when applied pre-exposure; no benefit post-exposure.
• Anti-aging, split-face RCT (Milani & Sparavigna, Clin Cosmet Investig Dermatol, 2018): 0.1% melatonin in lipospheres improved wrinkle appearance (p=0.05), skin microrelief (p=0.001), tonicity (p=0.05), and dryness (p=0.01) versus untreated control.
• Serum-in-oil trial (Goldberg et al., J Cosmet Dermatol, 2019): 103 women using melatonin + bakuchiol + ascorbyl tetraisopalmitate showed significant reductions in brown-spot count and area (p<0.05), wrinkle parameters (p<0.01), and improvements in firmness and elasticity (p<0.01).
• Antioxidant blend (Morganti et al., 2012): 0.0002% melatonin with vitamin E and beta-glucan produced significant gains in hydration, lipids, elasticity, and fine wrinkles (p<0.005) in aging skin.
• Radiation dermatitis (Zetner et al., 2023): In 172 breast-cancer patients, a 25 mg/g melatonin cream significantly reduced both incidence and severity of acute radiation dermatitis versus placebo — the largest randomized melatonin skin trial to date.
• Combined oral + topical (2025, n=39): 84-day regimen produced greater wrinkle-depth reduction (−18.5% vs −9.4%) than topical alone, suggesting a possible additive systemic effect.

A 2024 systematic review (Int J Mol Sci, 25:5167) confirmed that across randomized, double-blind, placebo-controlled work, pre-exposure topical melatonin reliably reduces UV and radiation-induced skin damage. The recurring limitations are small sample sizes, short durations, and the frequent use of combination formulations that obscure melatonin’s independent contribution — particularly for pigmentary endpoints.

Formulation Science for Topical Melatonin

• Solubility and delivery: Melatonin is poorly water-soluble and amphiphilic. Effective vehicles include glycol/ethanol systems, liposomes, nano-emulsions, and nanostructured lipid carriers. Liposomal and hyalurosome encapsulation improve both stability and penetration.
• Photostability: Melatonin degrades under light. Opaque or airless packaging, antioxidants (e.g., vitamin E), and a night-use positioning are practical mitigations.
• Concentration: The clinical literature spans 0.0002% to 12.5%. Cosmetic night products typically use 0.1%–1%. Dose-response data suggest meaningful photoprotection requires higher concentrations than typical cosmetic use.
• pH and compatibility: Melatonin is stable across a broad pH range; avoid strong oxidizing actives that accelerate its degradation.

Regulatory and Positioning Notes

Melatonin is permitted as a cosmetic ingredient in many markets at low concentrations, but it is regulated as a medicinal substance in some jurisdictions, and drug-like claims (sleep, medical photoprotection) are not permissible on cosmetic labelling. Formulators should verify market-specific limits and keep claims to cosmetic skin-appearance endpoints.

The Research Verdict

Topical melatonin has one of the more compelling mechanistic stories in modern skin science: a complete cutaneous synthesis system, dominant MT1 receptor biology, direct mitochondrial antioxidant action, and reproducible photoprotection in controlled human trials. Its anti-aging signals — hydration, elasticity, wrinkle depth — are consistent, if modest and heterogeneous. Its role in pigmentary regulation is biologically plausible and supported by tissue-level data, but not yet confirmed in controlled human pigmentary trials, and dose-dependent opposing effects mean brightening claims remain premature.

For 2026 formulators, the defensible positioning is a night-use, encapsulated antioxidant serum or cream built on melatonin’s photoprotection and mitochondrial science — with pigmentary or brightening claims withheld until the clinical record catches up with the mechanism.

References

1. Lerner AB, Case JD, Takahashi Y, Lee TH, Mori W. “Isolation of melatonin, the pineal gland factor that lightens melanocytes.” J Am Chem Soc. 1958;80(10):2587.
2. Slominski AT, Hardeland R, Zmijewski MA, Slominski RM, Reiter RJ, Paus R. “Melatonin: A Cutaneous Perspective on its Production, Metabolism, and Functions.” J Invest Dermatol. 2018;138(3):490–499.
3. Sevilla A, Chéret J, Slominski RM, Slominski AT, Paus R. “Revisiting the role of melatonin in human melanocyte physiology: A skin context perspective.” J Pineal Res. 2022;72(3):e12790. PMID:35133682.
4. Bangha E, Elsner P, Kistler GS. “Suppression of UV-induced erythema by topical treatment with melatonin. Influence of the application time point.” Dermatology. 1997;195(3):248–252. doi:10.1159/000245953. PMID:9407172.
5. Kleszczynski K, Fischer TW. “Melatonin and human skin aging.” Dermatoendocrinol. 2012;4(3):245–252.
6. Milani M, Sparavigna A. “Antiaging efficacy of melatonin-based day and night creams: a randomized, split-face, assessor-blinded proof-of-concept trial.” Clin Cosmet Investig Dermatol. 2018;11:51–57.
7. Goldberg DJ, Robinson DM, Granger C. “Clinical evidence of the efficacy and safety of a new 3-in-1 anti-aging topical night serum-in-oil containing melatonin, bakuchiol, and ascorbyl tetraisopalmitate.” J Cosmet Dermatol. 2019;18(4):1065–1071.
8. “Clinical Studies Using Topical Melatonin.” Int J Mol Sci. 2024;25(10):5167. doi:10.3390/ijms25105167.
9. “Melanogenesis Is Directly Affected by Metabolites of Melatonin in Human Melanoma Cells.” Int J Mol Sci. 2023. PMID:37834395.
10. “Concentration-dependent stimulation of melanin production as well as melanocyte and keratinocyte proliferation by melatonin in human eyelid epidermis.” Exp Dermatol. 2023;32(5):684–693. PMID:36601673.